1. Field of the Invention
The present invention relates to a fuel cell system and, more specifically, a liquid fuel cell such as a direct methanol fuel cell (“DMFC”), to which a solid polymer molecule electrolyte membrane is applied, directly employing a liquid organic compound, such as methanol, as fuel so as to generate electric power.
2. Description of the Related Art
As a fuel for a fuel cell, methanol is relatively cheap and can be easily dealt with. DMFC can employ the methanol without reforming to generate electric power. Therefore, compared with conventional fuel cells, DMFC has an advantage that a reformer for fuel thereof can be omitted and the constitution can be simple. Additionally, DMFC uses a solid polymer molecule electrolyte which is far more manageable than a liquid electrolyte such as a solution of sulfuric acid or potassium oxide. More specifically, DMFC has a performance advantage over the conventional fuel cells.
The solid polymer electrolyte membrane is necessary to be humidified with water. The water can be admixed to the methanol in advance so as to be supplied to the electrolyte membrane. However, in this case, an energy concentration of the fuel cell is decreased correspondingly with a degree of dilution of the methanol. To increase the energy concentration, there is proposed an art in which an exhaust from the fuel cell is recycled so as to employ water contained therein to humidify the electrolyte membrane.
A related art is disclosed in Japanese Patent Application Laid-open No. 2002-110199, in which an exhaust from a cathode and an anode is recovered and recycled.